1. Technical Field
The present invention relates to a package board, semiconductor package, and fabricating method thereof.
2. Description of the Related Art
Generally, a semiconductor chip is mounted on a printed circuit board to form a package. In a chip scale package (CSP), wafer level package (WLP), direct chip attachment (DCA) package, ball grid array (BGA) package, flip chip package, and through-hole package, the bumps of a semiconductor chip is electrically joined with the circuits of the board. Typically, the semiconductor chip is positioned with respect to the board such that the bumps and circuits are in alignment, which are attached by a technique of reflowing solder formed between the board and the semiconductor chip. In a flip chip package and a chip scale package, there is a space or gap between the chip and the board.
The semiconductor chip and the board are generally formed from different materials having different coefficients of thermal expansion. Therefore, due to the heat applied during the process of fabricating a semiconductor package, a substantial amount of deformation occurs in the electrical connections between the board and the semiconductor chip. Such an imbalance in thermal expansion degrades the performance of the semiconductor chip and weakens the connections between the chip and the board, to incur malfunctioning of the entire package. This phenomenon is more significant when the size of the semiconductor chip is increased.
To resolve such problems and improve reliability in the electrical connections of the board and the semiconductor chip, an underfill method is being used of filling the gap between the board and the chip with encapsulant. This method of fabricating a semiconductor package isolates the electrical connections from exposure to the ambient environment, and provides mechanical strength to the semiconductor package and allows it to resist dynamic and static mechanical loads. Also, the encapsulant removes heat from the semiconductor chip, and provides additional thermal conduction paths which reduce the temperature difference between the semiconductor chip and the board. As a result, the underfill process for a semiconductor package using encapsulant significantly increases the life span of the semiconductor package.